For years organizations like the Humane Society and Mercy for Animals have being going undercover at America's largest farms, using hidden cameras to show exactly how our food is produced. The footage hasn't been pretty.

Time after time they've caught workers beating and torturing livestock. So Big Ag returned fire, introducing bills in more than a dozen states that would criminalize undercover filming on farms.

What follows are the videos that spurred Big Ag's censorship campaign:

Willet Dairy, New York
Mercy for Animals caught employees kicking and shocking animals that wouldn't bend to their will. Supervisor Phil Niles is heard recounting an abuser's greatest hits: How he beat cows with wrenches, smashed their heads with two-by-fours, kicked them when they were too feeble to rise.

"Fucking kicking her, hitting her," he chortles while recalling one incident. "Fucking jumping off the top of the goddamned gate and stomping on her head and shit."

His video showed hens packed into cages the size of a filing drawer, where each creature spent life in a space with the dimensions of a single sheet of paper.

Carlson's job was to cull the dead, the 100 or so hens whose wings and feet became caught in the caging, leaving them to die of thirst or be trampled to death by their cellmates each day.

On the next page, see the video that made it illegal to expose in animal abuse Iowa.

Iowa Select, Iowa
After Iowa Select was stung by this video, it helped push a law through the Iowa legislature that effectively made exposing cruelty a greater crime than abuse itself. Those found guilty faced up to a year in jail, and felony charges for repeat offenses.

Whitter Stables, Tennessee
The Humane Society caught Tennessee horse trainer Jackie McConnell slathering caustic chemicals on the ankles of his animals. The pain causes them to lift their legs higher during horse competitions. Footage also showed workers whipping, shocking, and beating horses in the head with sticks.

The Tennessee legislature's response: Crack down on the people who would expose such a thing.

Hallmark Meat Packing Company, California
The turning point for activists seemed to arrive in 2007, after a Humane Society investigation of the Hallmark Meat Packing Company.

The Chino, California slaughterhouse was a major supplier to the nation's school lunch program, delivering beef to 36 states.

But the Humane Society's video showed "downer" cows -- those too frail or diseased to walk -- being pushed by forklift to slaughter. The practice is highly illegal, since sick animals heighten the risk of introducing E. Coli, salmonella and mad cow disease into the food supply.

When it came to light, the USDA issued the largest beef recall in the agency's history. Hallmark went bankrupt.

Conklin Farms, Ohio
The small dairy in Plain City, Ohio had just three employees. But it compensated for size with sadism.

The video -- watch it on YouTube -- with a worker repeatedly stomping on a cow's head. It goes on to show employees stabbing animals in the face with pitchforks, beating their heads with crowbars, punching cows in their udders and body slamming calves to the ground.

One worker is caught on tape exuberantly describing how "We beat the fuck out of this cow. We stabbed her... I beat that fucker till her face was this big around."